news.arc is one of the libraries that comes with arc, and is a branch of the source for Hacker News and the Arc Forum. It defines all of the functions related specifically to the news site, and is what allows you to run a clone of the forum. It's located in the lib folder of the anarki repo.
main.arc is the launch script I included in my arc-openshift repository. It just sets a few variables, and then launches the news server with the right parameters. It's located in the root directory of the arc-openshift repo.
Other files of interest are the arc libraries srv.arc and app.arc. srv.arc sets up a web server, and app.arc adds extra utilities for things like user management, etc.